Twin-clutch, twin-shaft, dual shaft, or dual clutch transmissions of the alternating shifting type are well known in the prior art. Various types of twin clutch transmissions have been proposed and put into practical use, particularly in the field of wheeled motor vehicles. Traditional twin clutch transmissions are of a type in which gears are parted into two groups, each group having an individual main clutch, so that the operative condition of each group of gears is carried out by selectively engaging a corresponding main clutch. Twin clutch transmissions are used in vehicles to improve the transition from one gear ratio to another and, in doing so, improve the efficiency of the transmission. The gears of each group are typically individually engaged so as to rotatably connect a transmission input shaft to a transmission output shaft for transmitting torque at differing ratios. The differing ratios may be engaged by multiple shift clutches. A typical dual clutch is illustrated in commonly owned U.S. Pat. No. 7,082,850, to Hughes, the disclosure of which is hereby incorporated by reference in its entirety.
In such transmissions, the main section may be shifted by means of a shift control system. Typical shift control systems include multiple actuators for engaging and disengaging the multiple shift clutches. The actuators may be pneumatic, electric, or hydraulic, and typically, one double acting actuator controls each shift clutch. The shift control system may also include a control logic for controlling the engagement of the main clutches, and the shift clutches to provide a desired gear ratio during vehicle operation. Generally, one ratio for each group may be simultaneously engaged with only one main clutch engaged during vehicle operation. To complete a shift in a dual clutch transmission, the engaged main clutch is disengaged as the disengaged main clutch is engaged. Accordingly, the disengaged group may be reconfigured as the engaged shift clutch is disengaged while another shift clutch of the group is engaged to provide a higher or low gear ratio to complete the next main clutch disengage/engage process.
Typical non-dual clutch transmissions may be shifted by a single actuator acting as a X-Y shift control device. A X-Y shift control device may be operated by a manual lever or by a pneumatic, hydraulic, or electrical control. Prior X-Y shift control devices are disclosed in U.S. Pat. Nos. 4,873,881 and 5,281,902, to Edelen, U.S. Pat. No. 4,899,607 to Stainton, and U.S. Pat. No. 6,227,067 to Steeby, which are assigned to the assignee of the present application, the disclosures of which is hereby incorporated by reference.